• Journal of the Korean Society of Safety
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• v.22 no.4
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• pp.20-25
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• 2007

Instrument transformers are a safe measurement device designed to measure high voltage and large current. A current transformer(CT) is a type of instrument transformer designed to provide a current in its secondary winding proportional to the current flowing in its primary. It is commonly used in metering and protective relaying in the electrical power industry where it facilitates the safe measurement of large current. But, care must be taken that the secondary of a current transformer is not disconnected from its load while current is flowing in the primary, as this will produce a dangerously high voltage across the open secondary, and may permanently affect the accuracy of the transformer. Especially, industrial disaster such as an electric shock and/or a burn accident occurs occasionally by disregard of warning or attention. In this paper, we developed the detector for open of current transformer secondary terminal, and which was tested by the Korea Electrotechnology Research Institute. Test results show that Current Transformer secondary Open Detector(CTOD) interrupted within one second electronically when the 2nd terminal of current transformer opened.

• Journal of Advanced Navigation Technology
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• v.16 no.6
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• pp.1014-1023
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• 2012

Recently with improvement of SMART Grid, AMI network security has been affecting the environment for Electric information and communication. The system and communication protection consists of steps taken to protect the AMI components and the communication links between system components from cyber intrusions. The addition of two way communications between SUN and HAN introduces additional risk for unauthorized access to the AMI system. In this paper, we propose new AMI device authentication infrastructure, key establishment and security algorithm based on public key encryption to solve AMI network security problems.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11c
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• pp.827-834
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• 2000

A granular herbicide applicator attached to conventional ride-on rice transplanter with 6 rows was developed in order to carry out both transplanting and herbicide application at once. It resulted in labor saving by 98%. The prototype is composed of a metering device and a spinning disc spreader. The application rate per 10a can be varied from 1 to 3 kg and the application swath is 1.8 m, which is the planting width of the ride-on rice transplanter with 6 rows. The angular speed of spinning disc and the application height were used as design factors to obtain the uniform distribution of herbicide granules. As the result of experiment, the distribution uniformity showed a tendency to be proportional to the increases of both spinner angular speed and application height. The prototype with angular speed of spinning disc of 7359 rpm and the application height of 20 cm was made and its distribution uniformity was relatively uniform with the CV(coefficient of variation) of 21.7%. In field test, when the tested herbicides such as ACl40+Stomp and Londax+YRC were applied, the weed control has continued for 65 days since transplanting was done.

• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.12-14
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• 2007

A voltage transformer (VT) is used to transform a high voltage into a low voltage as an input for a metering device or a protection relay. VTs use an iron core which maximizes the flux linkage. The primary current of the VT has non-fundamental components caused by the hysteresis characteristics of the iron core. It causes a voltage drop in the winding impedances resulting in the error of the VT. This paper describes a compensation algorithm for the VT. The proposed algorithm can compensate the secondary voltage of VT by calculating the primary current from the exciting current of the hysteresis loop in the voltage transformer. In this paper, the exciting branch was divided into a non-linear core loss resistor and a non-linear magnetizing inductor. The performance of the proposed algorithm was validated under various conditions using EMTP generated data. Test results show that the proposed compensation algorithm can improve the accuracy of the VT significantly.

• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.54-56
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• 2007

DLMS(Device Language Message Specification) 메시지 규약과 COSEM(Companion Specification for Energy Metering) 오브젝트 모델링 기법을 채택한 계량기 통신 및 오브젝트 모델 표준인 IEC62056은 계량기의 상호 운용, 관리, 보안 그리고 계략 데이터 모델링에 대한 방법 등을 기술하고 있으며 TCP-UDP, GPRS, PSTN등의 원격 접속을 위한 프로파일을 지원하고 있다. 본 논문에서는 DLMS계량기의 계량 데이터를 수집 및 관리하는 IEC6056 기반의 energy information concentrator(이하 EIC)를 제안한다 이 중계장치는 COSEM 오브젝트로 구성되어 있는 DLMS 계량기를 EIC의 논리장치로 모델링하여 등록 관리하는 새로운 개념의 DLMS 중계장치이다. 쉽게 말해서 IEC62056을 따르는 DLMS 클라이언트에서 EIC를 바라볼 때 여러 개의 논리 장치를 가지는 DLMS 장치로 인식이 된다. EIC는 특성상 기능적으로 크게 두 부분으로 나누어지는데, 상위 시스템과의 인터페이스를 담당하는 서버부분과 계량기로부터 데이터를 수집하는 클라이언트 부분이다. 서버 부분은 계량 데이터 오브젝트 관리 모듈 부분과 TCP/IP서버 모듈로 나누어지며 클라이언트 부분은 DLMS 계량기 스케줄링 부분과 DLMS 클라이언트 부분으로 나누어진다. 개발된 EIC는 최대 111대까지의 계량기를 지원 관리할 수 있으며, 각 1Mbit 용량의 오브젝트를 구성 할 수 있다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.8
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• pp.1457-1462
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• 2009

This paper proposes a compensating algorithm for the secondary voltage of a coupling capacitor voltage transformer (CCVT) in the time domain by considering the hysteresis characteristics of the core. The proposed algorithm estimates the three error terms i.e. the voltage across the secondary winding parameters, the voltage across the primary winding parameters, and the voltage across the capacitor and the tuning reactor. These three terms are added to the measured secondary voltage to obtain the correct voltage. The algorithm reduces the errors of the CCVT significantly both in the steady state and during a fault. The performance of the algorithm is verified under the various fault conditions by varying the fault distance, the fault inception angle, and the fault impedance with the EMTP generated data. Test results clearly indicate that the algorithm can increase the accuracy of a CCVT significantly under the fault conditions as well as in the steady state. The algorithm helps improve the performance of a protection relay or a metering device.

• The KIPS Transactions:PartA
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• v.18A no.6
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• pp.281-292
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• 2011

In this paper, a simulator adapted in AMI network environment with NS-2 was designed and implemented. The limited AMI operation environment such as processing times of data, network protocol and system performance can be simulated to find out the optimal AMI formations. Consequently, it is simulated under conditions that are closely analogous to the actual networks and each device. In future, the result of simulation would be applied to AMI network, mitigated the waste of resources and much contributed towards the real optimal AMI deployments in utilities.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.519-527
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• 1996

Most operation related to the application granular agrochemicals in korea are manual and labour consuming. As a multipurpose granular applicator, a pneumatic granular applicator that can be attached to conventional ride -on machines for paddy field was designed in this study. Experiments and simulations were carried out for determine in the design factors with one fertilizer (DongBu 21-17-17) and one pesticide (SamKong Ivi). The maximum terminal velocity of granular chemicals was estimated as 14.2m/s. A better distribution pattern was obtained at the diffuser having only deflectors without dividing guides. The diffuser spacing 1.0m for the fertilizer and the diffuser spacing 0.8m for the pesticide at the boom height over 0.80m were acceptable for the uniform distribution. In the case that the forward speed of ride-on machines was 0.7m/s, the groove opening and the roller speed of the selected metering device were13mm -15mm at 2 rps for the fertilizer, and 9 mm-11mm at 0.25rps or the pesticide. This study suggested a method of developing a pneumatic applicator for granular agrochemicals.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.3
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• pp.141-146
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• 2016

The AMR(automatic meter reading) system has been increasingly and widely used for its efficient and intelligent management, which is a technology that automatically collects consumption data from a water meter or energy metering device. The digital meter instead of the mechanical meter should be used in the system. Up to now, various types of sensor to measure the water flow rate have been used in the digital water meter, for example, reed switch, photo IR approximate sensor, ultrasonic sensor, electromagnetic sensor, etc. In this paper, a new sensing technology, where a variable capacitor and digital circuit were used for sensing the water flow rate, was proposed. The circuit was designed and verified by Pspice simulation. And a PCB board for the circuit was fabricated. After then, a prototype of digital water meter using a variable capacitor to measure the water flow rate was fabricated. The function tests of the fabricated digital water meter were performed, and it was found that the meter worked properly. Since the new technology has much better properties in terms of cost and power consumption compared to conventional technologies, it should be one of the major digital water meter technologies in the future.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.223-223
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• 2020

하천 조사에 드론의 필요성은 점차 증가하고 있으며, 하천시설 조사 및 하천 물리량 간접 계측 등에 있어서 활용성 또한 증가하고 있다. 드론을 이용한 하천시설 및 하천 조사는 주로 광학 영상에 기초한 간접 계측을 중심으로 활발히 기술 개발이 진행되고 있으며, 최근에는 적용하는 임무장비를 확장하여 초분광카메리나 LiDAR 등을 활용하려는 시도가 활발히 이루어지고 있으며, 관련 기술의 개발도 역시 급격히 진행되고 있다. 이러한 기술 발전을 통해 하천 조사에 있어서 간접 계측의 정확도는 계속하여 증가하고 있으나, 기술의 편리성이나 활용성에 비해 정확도 향상에는 어느 정도 한계가 있으며, 간접 계측에 의한 정확도를 확보하기 위해서는 여전히 직접 계측 결과와 비교를 통한 검보정이 필수적이다. 직접 계측은 첨단 계측기를 사용한다고 하더라도 아직까지 인력에 의한 의존도가 높으며, 측정 효율이 여전히 떨어지고 있어 간접 계측의 편리성을 저하시키는 원인으로 작용하고 있다. 본 연구에서는 드론 기반의 간접 계측이 편리성 및 활용성, 정확도를 올리 수 있는 무인 IoT 수질 측정기를 개발하고자 한다. 무인 IoT 수질 측정기는 드론에서 측정한 자료 검보정 자료 획득을 목표로 하며, 드론으로 측정한 지역에 대한 데이터 검보정 정확도를 향상 시킬 수 있는 측정방안을 고려하고 있으며, 현재 이용 가능한 IoT 통신 모듈의 적용성 및 통신 거리를 고려하여 개발을 진행하고 있다. 특히 데이터 전송을 고려하여 개별 통신 규약 검토를 진행하였으며, 각종 표준을 검토하였다. 통신을 위한 전력 소모를 고려하여 저전력 통신 모듈을 중심으로 검토를 진행하였으며, 하천의 특성을 고려한 수질 측정 지점 결정을 위한 측정 알고리즘을 개발하여 적용하였다.